Safety means for television tubes



June 8, 1937. K. SCHLESINGER 2,083,205

SAFETY MEANS FOR TELEVISION TUBES Filed Oct. 5, 1934 Recefw'n Patented June 8, 1937 UNETED PATENT GFFEQE Kurt Schlesinger, Berlin, Germany Application October 5,

1934, Serial No. 747,012

In Germany October 11, 1933 4 Claims.

The subject matter of the present invention is a means for safeguarding Braun tubes, and more particularly tubes for television purposes, against excess potentials occurring between control elec trode and cathode.

By reason of the close spacial disposal of the electrodes an inadmissible increase in potential, and accordingly flash-over, may occur in view of the relatively high potentials employed if switching elements, which are situated for example outside of the tube, are varied by any causes in their efiectiveness.

Television tubes, and more particularly gasfilled tubes, are extremely sensitive against excess potentials between control electrode and cathode.

The invention is described more particularly and conveniently with the assistance of the drawing, which represents a possible form of embodiment.

In the drawing there is shown a circuit ar rangement with Braun tube suitable for television reception, in which the cathode l is raised to a negative potential of approximately 2000 volts against the anode I l which is connected to earth, the control electrode 2 to a potential which is negative to the extent of approximately 10 volts as compared with the cathode. To the latter there is conducted the bias over a working resistance 3 of approximately 100,000 ohms, and the control currents over a condenser 4, the second armature of which is connected with earth through the medium of the receiving amplifier 5 with small inner resistance. It may occur that the condenser 4 (.5mf.) is ruptured. The charging of the electrode 2 then taking place to a few thousand volts positive in relation to the cathode I may result in destruction of the tube.

As a remedy there is employed for example according to the invention a glow-lamp 6 with small ignition potential, arranged in such fashion that its one electrode is linked up with the control potential 2. The other electrode of the glow lamp is connected with the cathode through the medium of a large condenser 9 of, say, 1 mf., and at the same time there is tapped at the resistance [0 of the mains-connection apparatus a bias of such nature that the glow lamp 6 is short 1y about to ignite. The initiation of the safety arrangement may be adjusted by varying this tapping. With suitable selection of the ignition potential the tapping may also be connected in direct fashion with the most negative pole of the anode potential source, whereby the condenser 9 may be dispensed with. Additionally there may be provided in accordance with the invention a series resistance 1 in the path of the speech line 8, which resistance is preferably selected to be large as compared with the resistance of the glow lamp 6 when ignited but small as compared with the impedance between the control electrode 2 and cathode l (i. e., for example 1000- 5000 ohms). In this manner safeguarding is effected against excess potential without cutting off any part of the frequency band.

I claim:

1. In a television reception arrangement the combination of a Braun tube, a receiving amplifier and a glow lamp, said Braun tube at least containing a cathode, a control electrode and an anode, said anode being connected to earth, said cathode being connected to a potential highly negative with respect to said anode, said control electrode being connected to a potential slightly negative with respect to said cathode, a condenser connected between said control electrode and one output terminal of said receiving amplifier, a second output terminal of said amplifier being connected to earth, said amplifier having a low output resistance, said glow lamp being connected between said control electrode and said cathode of said Braun tube.

2. In a television reception arrangement the combination of 2. Braun tube, a receiving amplifier and a glow lamp, said Braun tube at least containing a cathode, a control electrode and an anode, said anode being connected to earth, said cathode being connected to a potential highly negative with respect to said anode, said control electrode being connected to a potential slightly negative with respect to said cathode, a resistance and a condenser connected in series between said control electrode and one output terminal of said receiving amplifier, said resistance being large as compared with the resistance of the glow lamp when ignited but small as compared with the impedance between control electrode and cathode, a second output terminal of said amplifier being connected to earth, said amplifier having a low output resistance, said glow lamp being connected between said control electrode and said cathode of said Braun tube.

3. In a television reception arrangement the combination of a Braun tube, a receiving ampliher and a glow lamp, said Braun tube at least containing a cathode, a control electrode and an anode, said anode being connected to earth, said cathode being connected to a potential highly negative with respect to said anode, said control electrode being connected to a potential negative with respect to said cathode, a condenser connected between said control electrode and one output terminal of said receiving amplifier, a second output terminal of said amplifier being connected to earth, said amplifier having a low output resistance, said glow lamp being connected between said control electrode and said cathode of said Braun tube and means for biasing said glow lamp at a potential near the ignition potential for said lamp.

4. In a television reception arrangement the combination of a Braun tube, a receiving amplifier and a glow lamp, said Braun tube at least containing a cathode, a control electrode and an anode, said anode being connected to earth, said cathode being connected to a potential highly negative with respect to said anode, said control electrode being connected to a potential slightly negative with respect to said cathode, a resistance, and a condenser connected in series between said control electrode and one output terminal of said receiving amplifier, said resistance being large as compared with the resistance of the glow lamp when ignited, but small as compared with the impedance between control electrode and cathode, a second output terminal of said amplifier being connected to earth, said amplifier having a low output resistance, said glow lamp being connected between said control electrode and said cathode of said Braun tube, said resistance and said condenser being so selected that cutting ofi the frequency band of the receiving amplifier does not take place.

KURT SCHLESINGER. 

